perhaps there could be dragons that prefer swiming to flying and live in the seas and larger rivers of skyrim? they would have a more fishlike appearance and would terrorise the waters. they would still speak the language .
here is an example
http://www.deviantart.com/download/119351895/monster_hunter_plesioth_by_LynxKano.jpg
http://t0.gstatic.com/images?q=tbn:ANd9GcQTUn5ebMFG0PAWanoxGXFEyQbVodu3FSSBH2pGUv2S4cnmGTgH
http://i.imagehost.org/0519/Chinese_Dragon_Water_by_DracoApocalyptis.jpg
But perhaps we can have a type of dragon that partial burrys itself, pretends its something else and jumps out of the ground to ambush you?
anyways- a singular design would not be good, and with the normal dragons- could they atleast have different heads?